1. Field of the Invention
The present invention relates to an air damper, and more particularly, to an improvement of a cylinder type air damper preferably used for a glove box or the like of an automobile.
2. Description of the Related Art
A conventional cylinder type air damper preferably used for a glove box or the like of an automobile, is disclosed in Japanese Patent Application Laid-open No.8-105482.
Although it is not illustrated in the drawings, such a conventional damper comprises a cylinder whose opposite ends are opened, a piston movable in the cylinder, and a cap for closing one of the opening of the cylinder. The piston is provided with an orifice, and is formed at its peripheral surface with an annular recessed groove. A first O-ring which is narrower than a width of the groove, is fitted in the groove such that the first O-ring can move in a widthwise direction. A communication groove is formed in a bottom of the groove so that the communication groove is opened and closed by the movement of the first O-ring within the recessed groove. The cap is formed at its peripheral surface with a plurality of locking holes. By locking each projection provided on the cylinder to its corresponding locking hole, the cap can be mounted to the one end opening through a second O-ring. The other end opening of the cylinder is for allowing a piston rod to pass through the cylinder.
When this air damper is used in the glove box of the automobile, the cylinder is fixed to the side of the instrument panel, and a tip end of the piston rod projecting from the other end of the cylinder is fixed to the side of the glove box. If the glove box door is moved in an opening direction, the piston rod is gradually pulled out from the cylinder so that the piston is moved in the same direction in the cylinder. The glove box is thus reliably moved to an open position slowly by a flowing resistance of air passing through the orifice. In this case, the communication groove is closed by the movement of the first O-ring in the recessed groove.
When the glove box door is moved to close direction, the piston rod is gradually pushed into the cylinder so that the piston is moved in the same direction in the cylinder. The first O-ring is moved in the recessed groove to open the communication groove and release the air in the cylinder. Therefore, the piston is swiftly moved in the opposite direction in the cylinder to assist the closing operation of the glove box.
However, in such a conventional air damper, the second O-ring seal is required even when the cap is mounted to the one end opening. In addition, to secure the one-way system, the first O-ring seal must be movable fitted in the recessed groove of the piston. That is, two O-rings are required and the entire structure is thus complicated. Therefore, assembly is complex and not economical. Finally, if the first O-ring is moved in an inclined state in the recessed groove, the air damper may not be operated smoothly in some cases.